Transmitting apparatus



D. G. McCAA.

TENS TTING APPARATUS. APPLICATION FILED !AN.19, I920.

Patented June 21 192L [EMMY AWN 07 7 J UNITED STATES PATENT OFFICE.

DAVID G. MGGAA, OF LANCASTER, PENNSYLVANIA, ASSIGNOR OF ONE-HALF T0 CORNELIUS D. EHIRET, OF -MOUN'1' AIRY, PHILADELPHIA, PENNSYLVANIA.

TRANSMITTING APPARATUS.

To ell whom it may concern:

Be it known that I DAV-ID Gr. MQGAA, a citizen of the United States residing in the city of Lancaster, county of Lancaster, State of Pennsylvania, have invented a new and useful Transmitting Apparatus, of which the following is a specification.

My invention relates to apparatus for transmitting high frequency energy under control of a microphone or other signaling instrument whereby no energy will be impressed upon the natural or artificial medium extending between transmitting and receiving stations until sound waves .or speech are uttered into the microphone, or until other control is effected.

- For an illustration of one of the modes of practising my invention, reference is hadto the accompanying drawing, which is a diagrammatic view of transmitting apparatus embodying my invention and suitable for practising my method. 7 Refe'rrmg to the drawing, V is a thermiequivations preferably being high, as, for example, well above audibility.

The coils L and L couple the circuit of the anode a; with the circuit of the grid 9, the

filament f being supplied by current from battery I; and regulated by resistance r. In the plate or anode circuit is the battery 3 which may be shunted by the condenser C There is associated also in the aforementioned circuits the primary P and the variable condenser C.

lninductive relation with the prima P are the secondaries S and S so woun or connected that at a given instant of time they exhibit at similar ends similar polarities. In shunt to the secondaries are preferably employed the variabletuning condensers C and C for tuning the secondary circuits to the frequency of the oscillations in the primary P.

V is a thermionic or electronic amplifier comprising two anodes a and a and two grids g and g cooperating with a common filament when alhthe electrodes are placed in one evacuated vessel, as indicated it will be understood, however, that two separate amplifiers may be employed, each comprising filament, grid and anode.

, One terminal of each of the secondaries S and S is connected by conductor 1 with the cathode or filament f of the amplifier V The other terminal of the secondary S connects through the secondary S, which may be shunted by the ,variable condenser C and through the conductor 2. with the grid 9 Similarly, the other terminal of the secondary S connects through the secondary 5*, which may be shunted by a variable condenser C and through conductor 3 with grid 9 In the circuit of the anode a is the primary P of an oscillation transformer,

Specification of Letters Patent. Patented J 11113 21,1921.

Application filed January 19, 1920. Serial No. 352,465.

shunted by the tuning condenser C for tunplate circuits being adjustable by varying or adjusting the points on resistances r and 7- at which the anode circuits connect.

"With the apparatus thus far described,

with oscillations of suitable radio or carrier wave frequency existing in the primary P, there will be impressed upon the grids g and 9 similar and equal electro-motiveforces, whereby in the circuits of the anodes a and a there will be repeated oscillations of like radio or carrier wave frequenc Inductively related with the primaries T and l are the secondaries S and 5, connected in. the antenna system comprising the antenna A, tunin inductance L and earth connection E. when the apparatus is properly balanced, there will be no high frequency energy in theantenna circuit because of the opposed relations of the primaries P P and the secondaries S and S Coupled with the secondaries S and S" are the primaries P and P connected in circuit with the battery 6 and microphone on. When the microphone is at rest, normally the current from the'battery b is not varied, and therefore there is no inductive efiect by the primaries P and P upon their secondaries S and S and accordingly there is no high frequency.energy in the anand amplified in the primaries other simultaneously decreased in ampli-- tude. Accordingly, the inductive effect of I the primaries l? and P upon the secondaries S and S is no longer zero; the cumulative effect of the primaries upon the secondaries is such that there existsin the antenna system high frequency oscillations varying in amplitude in accordance with sound waves or speech.

Instantly the voice or sound waves cease at the microphone m, high frequency energy ceases in the antenna system; and similarly, instantly sound Waves or speech is initiated and continued at the microphone m, oscillations are present in the antenna system and var in accordance with speech.

at' I claim is:

1. The combination with a source of oscillations of high fre" uency, a primary traversed thereby, secon ari'es similarly inductively affected by said primary, thermionic devices comprising grid and anode circuits, said grids similarly afle'cted by said secondaries whereby the oscillations in the anode circuits are substantially equal, means in series with said secondaries controlled by sound waves for affecting said grids in opposite senses, a transmitting conductor, and a difierential coupling between said conductor and said anode circuits, whereby only when sound waves are present high frequency energy appears in said conductor.

2. he combination with thermionic devices each comprising a cathode, grid and anode, of a source of current common to their anode circuits, resistances connected across the terminals of said source and connected in series respectively, with the different anode circuits, an output circuit, and

- means in each anode circuit other than the resistance therein for affecting said output circuit.

3. The combination with a plurality of thermionic devices each comprising a cath ode, grid and anode, an output circuit, a differential coupling between said circuit and the anode circuits, a transformer primary traversed by fluctuating current, secondaries inductively coupled to said prima and connected, respectively, in ser1es wit said grids and for affecting their potentials in like senses, transformer secondaries in ser1es w1th' sa1d secondaries and sa1d ds and affecting the potentials of sa1d gm s 1n opposite senses, and signaling means coupled to said second named secondaries.

4. The combination with thermionic devices each comprising a cathode, grid and anode, of a. source of current common to their anode circuits, resistances connected across the terminals of said source and connected in series, respectively, with the different anode circuits, an output circuit, and an inductive'coupling between each anode circuit and said output circuit.

5. The combination with a plurality of thermionic devices each comprising a cathode, grid and anode, an output circuit, a differential coupling between said circuit and the anode circuits, a transformer primary traversed by fluctuating current, secondaries inductively coupled to said rimary and connected, respectively, in series with said grids and affecting their potentials in like senses, transformer secondaries in series with said'secondaries and said grids and affecting the potentials of said grids in opposite senses, a-nd a telephone transmitter coupled to said second named secondaries.

6. The combination with a plurality of thermionic devices each comprisin a cathode, grid and anode, of a source 0 current, resistances connected across saidsource connected in the respective anode circuits, an output circuit, and means in each anode circuit other than the resistance therein for affecting said output circuit.

7. The combination with a plurality of thermionic devices each comprising a cathode, grid and'anode, of a source of current, resistances connected across said source connected in the respective anode circuits,

means for varying the portionsof said resistances included in said anode circuits, an output circuit, and means in each anode circuit other than the resistance therein for transferring energy to said output circuit.

8. The. combination with a plurality of thermionic devices each comprising a cathode, grid and anode, said cathodes, grids and anodes disposed within the same evacuated chamber, of a source of current, resistances connected across the terminals of said source externally of said chamber and connected in the respective anode circuits, and means for varying the relative magnitudes of said resistances.

In testimony whereof I have hereunto affixed-my signature this 16 day of January, 1920.

DAVID G. MoOAA. 

